1. Field of the Invention
The present invention relates generally to a check valve, and more particularly, but not by way of limitation, to a pressurized check valve assembly positionable on a rotatable drill string for preventing drainage of fluid from a stand pipe and rotary hose of a drilling rig when fluid flow through the drill string is interrupted.
2. Discussion of Prior Art
When drilling oil and gas wells using a rotary drilling rig, drilling fluids are circulated down the drill pipe through the bit and up the outside of the drill pipe. Each time a section of drill pipe is added to the drill string it is necessary to halt or interrupt the flow of the drilling fluids through the drill pipe. In such instances, problems are encountered because of the tendency of the drilling fluid to drain from the stand pipe and rotary hose of the rig.
In an effort to resolve this problem ball valves have been incorporated into the drill string. However, the normal useful life of such ball valves is approximately 325 closures before the seats of the ball valve must be reworked, an expensive and time consuming procedure. For example, 325 connections of drill pipe are required to form a drill string operating at a depth of 9000 feet. That is, the ball valve must be actuated 325 times in order to interrupt the flow of drilling fluid through the drill string when each section of drill pipe is added to the drill string.
Because of the limited useful life of the before-mentioned ball valves, and the expense incurred in the reworking of such valves and replacing same during the drilling operation, a need has long existed for an improved valve assembly which can effectively prevent the drainage of drilling fluid from the stand pipe and rotary hose when the flow of drilling fluid through the drill string is interrupted; and where such valve assembly requires little maintenance and has an extended useful life. Further, because the drill string is rotated during the drilling procedure, it would be highly desirable that such a valve assembly be self-contained and automatically actuated in response to flow pressure of the drilling fluids injected into the drill string. It is to such a check valve assembly that the subject invention is directed.